1. Field of the Invention
The present invention relates to a recording medium cartridge in which an information recording medium, an inner rotor and a shutter are accommodated in a cartridge casing in a piled state. When the inner rotor is rotated, the shutter overlapped on the inner rotor is moved between a first position for closing an opening part provided in the cartridge casing and a second position for opening the opening part.
2. Description of the Related Art
As shown in FIGS. 31 to 33, as a recording medium cartridge 101, a recording medium cartridge of a type is known that an information recording medium 103, an inner rotor 104 and a shutter 105 are accommodated in a cartridge casing 102 in a piled state, and when the inner rotor 104 is rotated, the shutter 105 piled on the inner rotor 104 moves between a first position (see FIG. 31) for closing an opening part 106 provided in the cartridge casing 102 and a second position (see FIG. 32) for opening the opening part 106.
As shown in FIG. 33, the overlapping surface 107 of the inner rotor 104 and the shutter 105 is formed in a flat surface. The inner rotor 104 comes into contact with the shutter 105 in the substantially entire area of the overlapping surface 107.
Further, as shown in FIG. 34, the shutter 105 comprises a pair of shutter members 111 and 112. The shutter 105 is provided with first overlapped parts 114 and second overlapped parts 115 through first step parts 113 in the moving directions (directions shown by arrow marks A-B) of the shutter members 111 and 112 in mutually overlapping chord sides 111a and 112a of the pair of shutter members 111 and 112. When the opposed chord sides 111a and 112a of the pair of shutter members 111 and 112 are overlapped on each other, as shown in FIG. 35, on the upper surface side of the shutter members 111 and 112, the first overlapped part 114 of one shutter member 111 is continuously connected to the first overlapped part 114 of the other shutter member 112 through the first step parts 113. On the lower surface side of the shutter members 111 and 112, as shown in FIG. 36, the second overlapped part 115 of one shutter member 111 is continuously connected to the second overlapped part 115 of the other shutter member 112 under an overlapped state through second step parts 116. As shown in FIG. 31, the recording medium cartridge 101 has been known that the opening part 106 provided in the cartridge casing 102 for recording and reproducing data is designed to be closed. In the usual recording medium cartridge 101, the first step parts 113 and the second step parts 116 are formed in parallel with the opening and closing moving directions of the shutter members 111 and 112. (For instance, see Japanese Patent Application Laid-Open No. 2001-332054)
The above-described recording medium cartridge 101 has such problems as described blow.
(1) As shown in FIG. 33, since the overlapping surface 107 of the inner rotor 104 and the shutter 105 is formed on the flat surface, both the inner rotor 104 and the shutter 105 come into close contact with each other on the substantially entire area of the overlapping surface 107. Thus, a frictional resistance becomes large, which interferes with the smooth movement of the pair of the shutter members 111 and 112.
(2) As shown in FIG. 35, the first step part 113 as a boundary between the first overlapped part 114 of the first shutter member 111 and the first overlapped part 114 of the other shutter member 112 which are exposed on the upper surface side of the pair of the shutter members 111 and 112 and the second step part 116 between the second overlapped part 115 of the one shutter member 111 and the second overlapped part 115 of the other shutter member 112 which are exposed on the lower surface of the pair of the shutter members 111 and 112 as shown in FIG. 36 are vertically overlapped on each other. Accordingly, the rigidity of the overlapped parts is lowered. Further, since the second step part 116 and the first step part 113 are overlapped on each other, dust or the like is liable to enter through these step parts 116 and 113 from an external part.
(3) Further, as shown in FIG. 37, the first step parts 113 and the second step parts 116 are formed in parallel with the moving directions A-B of the shutter members 111 and 112. Accordingly, when the pair of the shutter members 111 and 112 are closed, the pair of the shutter members 111 and 112 move from respectively completely transverse directions of their first step parts 113 and second step parts 116. Thus, the first and second step parts 113 and 116 of the one shutter member 111 are finally overlapped on the first and second step parts 113 and 116 of the other shutter member 112 with a prescribed gap G as shown in FIG. 38. When the gap G is the smaller, a dust preventing effect becomes the more excellent. However, the gap G is too small, the first and second step parts 113 and 116 of the one shutter member 111 interfere with the first and second step parts 113 and 116 of the other shutter member 112 with each other due to a dimensional error generated when the pair of shutter members 111 and 112 are manufactured or due to an assembly error generated when the shutter members are assembled. Thus, the chord sides 111a and 112a of the pair of the shutter members 111 and 112 are incapable of being overlapped on each other. In order to avoid the interference of the step parts generated when the pair of the shutter members 111 and 112 is closed, the gap G may be set to be wide. However, when the gap G is wide, the dust or the like may be possibly enter the cartridge casing 102.